[Abstract] Lithium-ion batteries are widely
considered to have the following advantages: greater than energy; high specific
power; self-discharge; no memory effect; cycle characteristics of a good; quick
discharge, and high efficiency; wide operating temperature range; no
environmental pollution etc., so the power supply is expected to enter the
ranks of the best of the 21st century.
At present, electric bicycles can be used
in the following four power battery that VRLA maintenance-free batteries, gel
lead acid batteries, nickel metal hydride batteries and lithium ion batteries.
Currently on the market is able to provide
a large number of lead-acid batteries, lead-acid batteries have been 130 years
of history, it can be said is the most used batteries. It's reliable, mature
production technology, the price is low. Commercialized electric bicycles
currently use the vast majority of sealed lead-acid battery, no need to add
water use, maintenance-free. The main chemical reactions are:
PbO2 + 2H2SO4 + Pb ← charging, discharging → PhSO4 + 2H2O + PhSO4
Lead sulfate into lead-acid battery when
the charge lead sponge Yin and Yang in which the fixed component is released to
the electrolyte of sulfuric acid, respectively, into spongy lead and lead
oxide, sulfuric acid concentration in the electrolytic solution becomes larger
and larger; whereas discharge occurs when the spongy lead and sulfuric acid
electrolyte in a lead oxide anode and the cathode plate of the reaction into
lead sulfate, sulfuric acid and electrolyte concentrations continue to
decrease. When the lead-acid battery charging less, two plates of lead sulfate
yin and yang can not be completely converted into spongy lead and lead oxide
charge if a long-term shortage of lead sulfate crystals will cause that plate
curing, battery quality deterioration; whereas if overcharging of the battery,
oxygen generated at the anode is greater than the adsorption capacity of the
cathode, so that the inner pressure of the battery increases, causing gas to
leak out, reducing the electrolyte, the active substance may also lead to
soften or off, battery life is greatly shortened.
Lead-acid battery weight ratio of the
energy of 28-40 Wh / Kg, the volume ratio of energy 64-72 Wh / I, too heavy,
too big, and can provide less power, short life, as the power supply of
electric bikes in general can only use about a year, if performance is poor or
improper use of only two or three months. In addition, lead-acid batteries as
well as the depth of discharge capacity and low temperature discharge capacity
is poor, you can not fast charge (but has recently been some progress in the
study of lead-acid battery fast charge) and other shortcomings. Improved
lead-acid batteries - gel lead acid batteries with sulfuric acid electrolyte
gel electrolyte substitution, security, storage capacity, discharge performance
and other aspects of life than ordinary lead-acid batteries have improved. All
in all, however, in the long run, lead-acid batteries in electric vehicles
using poor prospects. Scrap lead-acid batteries can cause secondary pollution
due to waste, and this is one of the important reasons that some local
governments a lot of electric bikes on the road refused to support.
Gel lead acid batteries
Gel battery is a common liquid electrolyte
lead-acid batteries improvements. It uses a gel electrolyte, no free liquid
inside presence, in the same bulky electrolyte capacity, large heat capacity,
heat dissipation capacity, to avoid the battery generally easy to produce
thermal runaway phenomenon; low electrolyte concentration on the plate
corrosion weak ; uniform concentration, the acid stratification phenomenon does
not exist.
These improvements make it more important
than the performance of VRLA maintenance-free battery, for example: the use of
stable performance, high reliability, long life, ability to adapt to the
ambient temperature (high and low) and strong to withstand prolonged discharge
capacity, cycle discharge capacity, depth of discharge and high current
discharge capability, there is overcharge and over-discharge self-protection,
battery discharge may continue after 100% connected to the load, the charge can
still be restored to its original capacity within weeks and so on.
Nickel-metal hydride battery (Ni-MH)
Nickel-metal hydride battery is the battery
nineties emerged rookie family, is developing rapidly. Ni-MH battery electrode
reaction is:
Positive: Ni (OH) 2 + OH- = NiOOH + H20 +
e-
Negative: M + H2O + e = MHab + OH-Ni (OH) 2
+ M = NiOOH + MHab
It is nickel-cadmium batteries and alkaline
batteries belong only to the hydrogen occlusion alloy material (mh) to replace
nickel-cadmium batteries in the anode material cadmium cd, electromotive force
is still 1.32v. It has all the excellent properties of nickel-cadmium
batteries, but also higher than the energy density of nickel-cadmium batteries.
The main advantages are: energy is higher than (a single charge can be
exercised long distance); high specific power, high current work in smooth
discharge (accelerating gradeability good); good low-temperature discharge
performance; long cycle life; safe, reliable, maintenance; no memory effect;
environment there is no pollution, renewable use, in line with the sustainable
development concept. However, Ni-MH battery is too costly and expensive.
Lithium-ion batteries
Lithium is the lightest metal world, when
constituting the battery, the output voltage is nearly 4v. Lithium ion
batteries are 1990 by Sony Corporation of Japan to market the first new type of
high-energy batteries. The advantage is the high specific energy of the battery
is more than the current highest energy. Application has access to the
information in portable products. 1995, Sony has developed a lithium-ion battery
for the electric vehicle successfully divided into two types: one is a pure
electric vehicle (EV) capacity of 100Ah cylindrical single cell, called a
high-energy lithium-ion battery; another is for a hybrid (HEV), the capacity of
22Ah, 8 series-connected to the battery module, but its output power is 2.7
times that of the former, known as high-power lithium-ion batteries.
High-energy battery was installed in 1996 at the Nissan Motor Company's first
car developed a lithium-ion electric car (Nissan Al-traEV), in Beijing the
first international exhibition of electric vehicles on display. The car on a
single charge can travel 200km, a top speed of 120Km / h.
Lithium-ion batteries are widely considered
to have the following advantages: greater than energy; high specific power;
self-discharge; no memory effect; good cycle characteristics; quick discharge,
and high efficiency; wide operating temperature range; pollution-free, so
expected to enter the ranks of the best power supply in the 21st century.
Expected during 2006 to 2012, when the further development of the lithium-ion
battery, MH / Ni battery market share will shrink. Lithium-ion market share
will expand. Currently there are already using lithium-ion batteries for
electric bicycles sold.
Since the nickel-metal hydride batteries
and lithium ion batteries are green batteries, will not cause secondary
pollution due to waste, environmental authorities likely to be accepted, and
there is a good export prospects, although currently more expensive, there is
still much room for price cuts, it should be strongly advocated.
General Electronics Battery Co., Ltd. electric vehicle battery has
been committed to the development, production, for consumers to create a safe,
environmentally friendly batteries.
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